MS Excel - Example No. 3
1. Input sample data into a table (cells B3:B12 and C3:C12); calculation of mean value (average) of sample: in the cell B13 call menu Insert - Function - Statistical - AVERAGE; calculation of standard deviation (SD) for sample data: in cell B16 call menu Insert - Function - Statistical - STDEV (see examples 1, 2).
F-test calculation: in the cell B15 call menu Insert - Function - Statistical - F-test:
2. Into field Array 1 in dialog window input cells for calculation - B3:B12 , into field Array 2 input cells C3:C12 (it is possible to mark them by means of mouse), push the button OK to get result:
3. Result of F-test: p=0.09675 indicates the probability of null hypothesis about homogeneity of variances (= probability of a error). As calculated p > 0.05, it means that difference between variances is statistically insignificant (H0: s1=s2 is true).
Calculation of unpaired t-test: in the cell B17 call menu Insert - Function - Statistical - TTEST:
4. Into field Array 1 in dialog window input cells for calculation - B3:B12, into field Array 2 input cells C3:C12 (it is possible to mark them by means of mouse), in Tails: 2, in Type: 2 (Two-sample equal variance - according to the result of F-test); push the button OK to get result:
5. Displayed results of calculations:
6. Result of t-test: p=0.005589 indicates probability of null hypothesis about equality of means (= probability of a error). As calculated p < 0.01, it means that difference between tested means is statistically highly significant.
Conclusion: Preparations tested don´t have the same effects on Mg level in blood serum of horses. The difference between effects of preparations is statistically highly significant (p<0.01).